This invention relates to the packaging of dry particulate foods such as ready-to-eat (xe2x80x9cRTExe2x80x9d) cereal. More specifically, this invention relates to an apparatus and processes for preparing lined cartons of the type known as a bag-in-a-box. The cartons are produced by beating a carton having a filled and sealed liner therein such that the liner expands to contact an interior wall of the carton and is adhered to the interior wall by an adhesive disposed there between. In a preferred embodiment, the carton has a reclosable dispensing means or pour spout which is connected to the liner or bag in such a way that a portion thereof is separated from the liner upon initial opening of the dispensing means to provide access to the contents of the carton.
The apparatus of the invention have an infeed airlock infeed section, a central sealing section under vacuum, and a discharge airlock section. Cartons having filled and sealed liners pass through each of these sections via a conveyor, and the bag is adhered to the carton interior in the central section. In operation, there are three cartons at different stations of the apparatus at any given time; a first carton in the discharge airlock station which is the finished carton, that is, the liner has already been sealed tot eh carton; a second in the central sealing section which is being processed to bond the liner to the carton, and a third in the infeed airlock station which is the xe2x80x9cnewxe2x80x9d carton which will be passed to the central sealing section to bond the liner to the carton. These are numbered in accordance with the process flow direction of the apparatus.
The use of cartons with liner bags for dry particulate products such as RTE cereal is well known. Such cartons are usually formed from a blank of paperboard or similar material comprising sidewalls with top and bottom flaps. The liner is a plastic or coated paper bag which holds the particulate product. The liner can be filled and sealed before or after being placed inside an open carton, the flaps of which are then folded and sealed.
Access to the contents of such cartons involves breaking the seal between the top flaps of the carton and pulling open the sealed liner bag. Resealing is often difficult and incomplete leading to a loss of freshness of the product. RTE cereal, for example, has a low moisture content and readily absorbs moisture from the air leading to a loss of crispness.
Dispensing devices such as pour spouts have been proposed to control the discharge of particulate product and minimize exposure to the atmosphere. However, when a carton with a pour spout contains a filled and sealed liner bag, the bag must be manually torn or cut with a knife or scissors when the spout is first opened. This arrangement has several drawbacks not the least of which is manually cutting or tearing of the liner bag. Once opened, and as the contents are depleted, the liner bag and its contents slide and shift positions in the carton which can cause the opened portion of the liner to become misaligned with the pour spout opening thereby hindering dispensing of product from the carton. This also causes product to drop between the carton and the liner.
Bag in the box type cartons and lined cartons in general are prepared using a variety of methods. Vacuum and induction heating are typical steps in such processes. For example, U.S. Pat. No. 2,998,788 to Back et al. disclose applying pour spout to the interior of liner in empty container. The spout is sealed to the inside of liner via a heated anvil. U.S. Pat. No. 4,918,906 to Ako discloses a package making system wherein bags are assembled within cartons, and U.S. Pat. No. 5,031,380 to Ueda discloses a package assembly system which includes a first container forming unit having a jaw, which includes a high frequency coil serving as a heater. U.S. Pat. No. 3,338,020 to McGee discloses a process of lining a container with plastic using vacuum. U.S. Pat. No. 4,723,935 to Furukawa discloses the use of air streams (vacuum) to force a lining against the inside of a carton or box. U.S. Pat. No. 4,095,390 to Knudsen discloses a manufacturing system wherein lids are placed on containers and sealed thereto as the assembled units travel past an induction heating area. The induction coil generates eddy current heat in a metal foil layer in the lid and thus welds to the container.
U.S. Pat. No. Reissue 33,467 to Steck et al. describes a machine for assembling filled containers of polyfoil wherein sealing jaws include induction coils used to induce a current in the metallic layer of the polyfoil to seal the container. The patent also shows an apparatus to carry out this operation.
U.S. Pat. No. 4,846,774 to Bell discloses a lid for a container which consists of a rigid ring and a removable membrane. The membrane, which includes a thin layer of aluminum, is welded (using induction heating) to the ring. Bell also discloses an apparatus to assemble the ring and membrane.
The existing approaches are limited in that the resulting packages provide limited protection of the package contents product from ambient moisture.
The present invention is therefore directed towards apparatus and methods for producing improved bag-in-a-box cartons where the bag or liner is physically adhered to the interior wall or walls of a sealed carton without breaking the seal of the liner. Thus, the liner will be prevented from slipping to the bottom of the carton. In preferred embodiments, the liner is adhered to the interior of the carton in such a way so as to provide placement of a reclosable pour device which readily facilitates initial opening or piercing of the package, yet offers superior protection from ambient moisture.
More specifically, the present invention is related to an apparatus sealing a filled liner to the interior of a dispensing assembly located in an end wall of a sealed carton containing said filled liner without breaking the seal of the filled liner. The apparatus includes a central sealing section connected to a vacuum source and having means for sealing positioned therein to align with the end wall of the carton. Infeed airlock and discharge airlock communicate with the central sealing section, and a conveyor moves the sealed cartons from the infeed airlock through the central section in sealing contact with the end wall and into the discharge airlock while maintaining a vacuum atmosphere in said central section. Using this apparatus, the liner is sealed to the interior of said dispensing assembly without breaking the seal of said liner.
The infeed airlock and outfeed airlock include a top and bottom conveyor which are adjustable to the carton size. Typically the top belt is raised or lowered to accommodate the specific carton to be processed. The conveyors are of sufficient length to maintain control of several boxes at a given time. Cartons are kept in the infeed and outfeed airlocks to block the flow of air and to aid maintaining vacuum inside the central portion.
Sensors in the airlock sections detect the presence of a carton. Upstream of the airlock is an additional sensor which can determine of sufficient cartons are available to maintain a continuous flow. During a continuous run, there are three cartons in the apparatus at any given point in time, a finished carton in the discharge airlock section, a second in the central sealing section and a third in the infeed airlock section. A full stream of cartons assists the airlocks to maintain vacuum along the working zone. When an upstream sensor detects that no more cartons are available, the infeed airlock stops with several cartons in it such that the vacuum is maintained in the working zone and the outfeed airlock continues to cycle until the working zone is clear, which is determined by a sensor at the beginning of the outfeed airlock. At this time, the cartons stop in the outfeed airlock to maintain vacuum. When the upstream sensor determines that cartons are again present, the infeed airlock starts in synchronization with the flow of cartons such that a full load of cartons is maintained in the airlock. As cartons approach the exit end of the working zone as determined by a senors at the beginning of the exit airlock, the outfeed airlock starts in harmony with the flow of cartons such that the outfeed airlock is always full. This system of sensors and conveyors ensures that three cartons in various stages of completion are in the apparatus at any given time as described supra.
This sequence also helps to maintain a level vacuum in the working zone. In the working zone, an induction coil is provided which creates the electric field to heat necessary to develop the currents to heat the foil target in the package. Once the foil reaches the appropriate temperature, the force created by the vacuum inflates the bag inside the box which sets the seal between the liner and the fitting.
Preferably, spaced lateral conveyors contact opposite sides of the cartons and feed them in a downstream direction. The lateral conveyors are positioned at right angles to the horizontal conveyor belt form a tight fit with the cartons to maintain a vacuum in all three sections.
To prepare the cartons of the present invention, a sealed carton having a sealed filled liner bag contained therein is conveyed into the infeed airlock section and fed into the central sealing section via the conveyor. In the central sealing section, the liner is adhered to the dispensing assembly of the carton and/or an end wall of the carton by application of bonding energy, e.g., RF frequency or heat, to activate a hot melt adhesive or other activatable adhesive or bonding material. The central sealing section is maintained under vacuum, with a vacuum pump for example, such that the pressure inside the bag is greater than the pressure in the sealing chamber. The bag typically has xe2x80x9cdead spacexe2x80x9d therein, that is, space filled with air rather than product, allowing the bag to expand outwardly and press against the interior of the carton and against the heated adhesive, causing the bag to bond to the interior wall of the carton and a pour spout that has been affixed to an interior wall of the container. The sealed, lined carton is removed from the apparatus by the conveyor and transported from the central sealing section through the discharge airlock, where the finished carton is then ready to be further processed for shipping.
In a preferred embodiment, the central sealing section includes a liner expansion area and a heating area, both of which are contained in the same housing. The carton will first pass through the expansion area to allow the bag to inflate under vacuum tight against the interior of the carton, particularly in areas or portions of the bag to be bonded to the carton. Once expanded, the carton adhesive is heated to an appropriate temperature such that the liner is adhered to the carton. The carton is then discharged through the airlock for further processing.
In the preceding embodiment, the adhesive is a heat-activated adhesive. In alternative embodiments, the adhesive may be activated by alternative physical means, e.g., by radiation of appropriate frequency. In such embodiments, a means for providing such radiation will replace the heat source of the heating zone, the controlling factor being appropriate bonding of the liner to the carton.
In other preferred embodiments, a shaking or bumpy conveyor is used to settle the contents of the liner before entering the infeed section.
Preferred cartons prepared with the apparatus described herein preferably have a reclosable pour device having a dispensing flap or pour spout which comes into contact with the filled, sealed liner when it is placed in the container such that the liner to the dispensing flap in such a way that the bag remains sealed, but upon initial opening of the flap, that portion of the liner bonded to the flap separates from the liner to provide access to the contents of the carton. Suitable cartons having pour spouts are disclosed in U.S. Ser. No. 09/213,100 filed Dec. 17, 1998.
It is preferred that the liner is bonded to the dispensing flap and to the area adjacent the periphery of the dispensing flap to maintain a tight seal upon closing of the flap. Moreover, the liner remains bonded at the bottom of the dispensing opening (i.e. along the pivot axis) to maintain alignment, and preferably the liner is also bonded such that it is congruous with the carton to the edges defining the pour opening to prevent product from falling between the bag and the box.
It is preferred to heat seal the liner to create a weakened tear line in the liner, but without breaking the seal of the liner, to facilitate initial opening of both the flap or pour spout and the liner. The tear lines are in the vicinity of and preferably congruous with the tear lines of the dispensing flap to facilitate opening and to maintain tight seal upon reclosure.